Hi there
I have just read again the Air Caraïbe report to see how the crew reacted to the cascade of fault reports, subsequent deprievation of flight protections, and how they applied the relevant procedures. There are french speaking people here who can translate any cryptic part of this report in French.
Phase 1 (22:11) "Weather deviation procedure for oceanic controlled airspace" (modification of the flight level, without result, back to initial FL)
Phase 2 (22:22) the "severe turbulence" QRH 5.01 procedure is implemented (A/THR off, N1 between 0.81 and 0.82)
Phase 3 (between 22:22 and 22:23) freezing of the Pitot probes
CAS plunged rapidly from 273 kts to 75 kts
ECAM messages: AUTO FLT AP OFF, MASTER WARNING (cavalry charge), F/CTL ADR DISAGREE, F/CTL ALTN LAW, F/CTL RUD TRV LIM FAULT, etc etc
Between 22:23 and 22:24: STALL, CRICKET and MASTER WARNING
Between 22:23 and 22:24: CAS goes back from 111 kt to 275 kt, ALT from 34200 ft 34500 ft
The crew struggled with the new multiple tasks to implement, and with the application of the QRH "unreliable speed indication": they had not the time to implement the "AFFECTED ADR IDENTIFICATION" and more worrying (I think), the "TECHNICAL RECOMMENDATIONS" in 2.22 state:
"RESPECT STALL WARNING AND DISREGUARD "RISK OF UNDUE STALL WARNING" IF DISPLAYED ON ECAM" and in the 3.02.54 (page 17) of the QRH: RELY ON THE STALL WARNING THAT COULD BE TRIGERRED IN ALTN OR DIRECT LAW. IT IS NOT AFFECTED BY UNRELIABLE SPEEDS BECAUSE IT IS BASED ON ANGLE OF ATTACK"
The Captain was concinced that the STALL ALARMS were irrelevant and took on him to ignore the "RELY ON THE STALL WARNING THAT COULD BE TRIGERRED IN ALTN...."
The Qantas crew was helped by the technical teams on ground to take the good decisions (and they had the time to do so)
I am not a specialist of air safety & procedures, but I feel very weird that fundamental warnings or alarms can have a variable meaning/reliability according to the context, and also very confusing that a crew already struggling with the instruments, not knowing exactly which one is valid, which one is corrupted, also may find ambiguities in the QRH.
Jeff
source:
http://www.eurocockpit.com/docs/ACA.pdf